EVALUATION OF THE TOXICOLOGICAL RISK ASSOCIATED WITH THE USE OF POLYACRYLAMIDES IN THE RECOVERY OF NUTRIENTS FROM FOOD-PROCESSING WASTE-(I)

Trivalent metal ions such as iron and aluminum are currently employed to flocculate liquid-borne solids from food-processing waste streams. These captured nutrient-rich waste solids are disposed of mainly through land applications (e.g., subsoil injection) because of the potential toxicity associated with the metal salts. Low-toxicity, water-soluble polyacrylamide polymers are currently approved for and employed as flocculants in potable water applications. The use of these polymers in food-processing waste streams could enable the captured solids to be recycled as components of animal feed, thus decreasing the burden on landfills and making good use of the proteinaceous matrix. However, polyacrylamides contain very low concentrations of acrylamide monomer, which is highly toxic and can cause neurotoxicity, cytogenic lesions, and an increase in tumor rates in experimental animals. With use of two industrial food processing wastes, experiments were conducted to determine how acrylamide monomer would partition during a solids/liquid separation and subsequent rendering. Based on the analytical data, 96% of the acrylamide monomer was measured in the water portion after separation. Because of background interferences, acrylamide could not be directly measured in the solids portion. With use of these results and worst-case calculations, <2 ppb of acrylamide could be present in animal feed, thereby making the associated risk de minimis.